1. Technical Field of the Invention
The present invention relates to a reverberation applying apparatus, a reverberation applying method, an impulse response generation apparatus, an impulse response generation method, a reverberation applying program, an impulse response generation program, and a recording medium for applying a reverberation effect to an audio signal in order to reproduce musical performances and the like held in acoustic spaces such as an auditorium a concert hall, a theater, and the like.
2. Prior Art
In recent years, various technologies are proposed so that a user can listen to realistic music in his or her room (hereafter referred to as a listening room) at home as if he or she were enjoying live performance in a concert hall or theater. One example is the acoustic field reproduction technology that reproduces acoustic fields of a virtual acoustic space such as a public concert hall in an actual acoustic space such as a private listening room.
The acoustic field reproduction technology will now be described. FIG. 11 schematically shows how sounds are reflected in an acoustic space 90 when a sound generation point S such as a musical instrument generates a sound. As shown in FIG. 11, sounds generated from the sound generation point S on a stage 901 are reflected on boundary surfaces such as a ceiling and side walls in the acoustic space 90 and reach an auditorium 902. The reflected sounds reach the auditorium 902 not simultaneously, but with time delays dependently on diverse travel distances.
In FIG. 11, a listening room L is depicted in the auditorium 902. If acoustics of a direct sound or a reflected sound (i.e., reverberant sound) can be reproduced on boundary surfaces such as a ceiling and walls in the listening room L, the listening room L can reproduce the acoustic field of the auditorium 902 enclosed in the listening room L. Generally, the reproduction of acoustics uses a reverberation applying apparatus that performs a convolution operation for an audio signal and an impulse response in the acoustic space for output. The impulse response is derived by using an acoustic signal containing reverberant sounds collected in the listening room L when the sound generation point S having nondirectional characteristics generates an acoustic measurement signal such as an impulse sound.
The conventional reverberation applying apparatus does not always accurately reproduce acoustic fields in the acoustic space. For example, it is impossible to reproduce an acoustic field in which the performer plays a musical instrument having specific directivity such as a brass instrument.